Engineering Escherichia coli for renewable benzyl alcohol production

Benzyl alcohol is an aromatic hydrocarbon used as a solvent and an intermediate chemical in the pharmaceutical, cosmetics, and flavor/fragrance industries. The de novo biosynthesis of benzyl alcohol directly from renewable glucose was herein explored using a non-natural pathway engineered in Escherichia coli . Benzaldehyde was first produced from endogenous phenylpyruvate via three heterologous steps, including hydroxymandelate synthase (encoded by hmaS ) from Amycolatopsis orientalis, followed by ( S )-mandelate dehydrogenase (encoded by mdlB ) and phenylglyoxylate decarboxylase (encoded by mdlC ) from Pseudomonas putida ATCC 12633. The subsequent rapid and efficient reduction of benzaldehyde to benzyl alcohol occurred by the combined activity and native regulation of multiple endogenous alcohol dehydrogenases and/or aldo-keto reductases. Through systematic deletion of competing aromatic amino acid biosynthesis pathways to promote endogenous phenylpyruvate availability, final benzyl alcohol titers as high as 114±1 mg/L were realized, representing a yield of 7.6±0.1 mg/g on glucose and a ~5-fold improvement over initial strains.